The structure was discovered on April 29 by archaeologist Hector Escobedo of the Universidad de San Carlos de Guatemala and graduate student Juan Carlos Melendez.

It lies at the base of the site's largest pyramid, which is about 60 feet (18 meters) tall.

Escobedo is co-director of the Waka' Archaeological Project with David Freidel, an archaeologist at Southern Methodist University in Dallas, Texas.

"We are trying to identify the remains, which appear to be in good condition despite the collapse of the tomb's roof," Freidel wrote on his Web site.

"This may be the resting place of either the dynasty founder, a man we do not have a history for, or K'inich B'alam the First, the Maya king who allied with Siyaj Ka'k', conqueror of Tikal [a major Maya city] in AD 378."

"Sounds Exciting"

Archaeologists believe the site of Waka'located in Laguna del Tigre National Park and also known as El Perucontrolled trade along the San Pedro Matir River.

At the city's height, tens of thousands of people may have lived there. Over the course of 700 years, 22 kings ruled.

Oil prospectors discovered Waka' in the 1960s. It contains 672 structures and several smaller houses.

Harvard University archaeologist Ian Graham mapped the site in the 1970s, and Freidel and Escobedo are the first to excavate there.